Method of fabricating display device

ABSTRACT

To achieve promotion of stability of operational function of display device and enlargement of design margin in circuit design, in a display device including a pixel portion having a semiconductor element and a plurality of pixels provided with pixel electrodes connected to the semiconductor element on a substrate, the semiconductor element includes a photosensitive organic resin film as an interlayer insulating film, an inner wall face of a first opening portion provided at the photosensitive organic resin film is covered by a second insulating nitride film, a second opening portion provided at an inorganic insulating film is provided on an inner side of the first opening portion, the semiconductor and a wiring are connected through the first opening portion and the second opening portion and the pixel electrode is provided at a layer on a lower side of an activation layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor element (typically, atransistor) and a manufacturing method thereof, and more specificallybelongs to a technique of a display device using a thin film transistoras a device. That is, the present invention belongs to a techniqueconcerning a display device represented by a liquid crystal displaydevice, an electroluminescence display device, or the like, a techniqueconcerning a sensor represented by a CMOS sensor or the like, and othertechniques concerning various semiconductor devices in which asemiconductor integrated circuit is mounted.

2. Description of the Related Art

In recent years, the development for a liquid crystal display device andan electroluminescence display device in which thin film transistors(TFTs) are integrated on a glass substrate has been progressed. Thesedisplay devices each are one of semiconductor devices characterized inthat thin film transistors are formed on a glass substrate using a thinfilm formation technique and a liquid crystal element or anelectroluminescence (hereinafter referred to as just an EL) element isformed on various circuits composed of the thin film transistors, sothat a function as a display device is provided.

The circuits composed of the thin film transistors cause unevenness tosome extent. Thus, when a liquid crystal element or an EL element isformed on the circuits, a leveling processing using an organic resinfilm or the like is generally conducted. Each pixel which is provided ina display portion of a display device has a pixel electrode therein. Thepixel electrode is connected with the thin film transistor through acontact hole provided in the above-mentioned organic resin film forleveling.

However, the following facts are found by the studies of the presentapplicant. That is, when a resin film is used as an interlayerinsulating film and a contact hole is formed using a dry etchingtechnique, threshold voltages (Vth) of the completed thin filmtransistors are greatly varied. For example, data shown in FIGS. 4A and4E are results examined with respect to a variation in thresholdvoltages of thin film transistors formed on an SOI substrate. In thedrawings, a black circular mark indicates the case where a laminatestructure of a silicon nitride film (SiN) and an acrylic film is usedfor the interlayer insulating film. In addition, an outline triangularmark in the drawings indicates the case where a laminate structure of asilicon nitride oxide film (SiNO) and a silicon oxynitride film (SiON)is used for the interlayer insulating film. In any case, the dry etchingtechnique is used for the formation of the contact hole. Note that“SiNO” and “SiON” are separately used according to the meaning in whichthe former contains the amount of nitrogen larger than oxygen and thelatter contains the amount of oxygen larger than nitrogen.

The datas shown in FIG. 6A and FIG. 6B are graphs obtained by evaluatinga variations in threshold voltages using statistical processing. Theordinate indicates a channel length (carrier moving length) and theabscissa indicates a Vth variation. In recent years, “quartiledeviation” has been known as statistical processing. The quartiledeviation is a difference between a value of 25% and a value of 75% in anormal probability graph and has been noted as statistical processingwhich is not influenced by an abnormal value. The present applicantdefines, based on the quartile deviation (which is also called 25percentile deviation), a difference between a value of 16% and a valueof 84% as 16 percentile deviation, and plots its value as “a Vthvariation” in the abscissa. Note that the 16 percentile deviationcorresponds to ±6 in a normal probability distribution. Thus, values,which are assumed as ±36 by respectively multiplying by factors, areused for data plotting. When an acrylic film is used as an interlayerinsulating film, as seen from the data, a variation in an n-channel TFTis about 4 times and a variation in a p-channel ITT is about 2 timesthose of the case not using the acrylic film. Thus, it is apparent thata variation is large in the case where the acrylic film is used. Thepresent applicant estimates that a charge is captured in the acrylicfilm by plasma damage in dry etching, thereby providing a cause ofvarying a threshold voltage.

SUMMARY OF THE INVENTION

The invention has been carried out in view of the above-describedproblem and it is a first problem thereof to provide a technology offabricating a thin film transistor without dispersing threshold voltagethereof in fabricating a display device in which an organic resin filmis used as an interlayer insulating film to thereby achieve to promotestability of operational function of the display device and enlargedesign margin in circuit design. Further, it is a second problem thereofto provide a fabricating process preferable in reducing the number ofsteps of the technology to thereby achieve to reduce fabricating cost ofa display device, particularly, a light emitting device.

The invention is characterized in resolving the first problem by thefollowing means. That is, the invention is characterized in using aphotosensitive organic resin film (preferably, photosensitive acrylicfilm, particularly, positive type photosensitive acrylic film) as anorganic resin film, forming a first opening at the photosensitiveorganic resin film, thereafter forming an insulating nitride filmcovering the first opening, forming again a second opening at theinsulating nitride film by using a photoresist and electricallyconnecting an upper electrode and a lower electrode present to interposethe organic resin film.

Means for resolving the first problem (hereinafter, referred to as firstaspect of the invention) will be explained in reference to FIGS. 3A and3B. In FIG. 3A, notation 101 designates a substrate, notation 102designates a base film, notation 103 designates a source region,notation 104 designates a drain region, notation 105 designates achannel forming region and these are constituted by using semiconductorfilms provided above the film 102. Further, notation 106 designates agate insulating film, notation 107 designates a gate electrode andnotation 108 designates a first passivation film. Heretofore, astructure of a publicly-known thin film transistor is shown and withregard to materials of respective portions, all of publicly-knownmaterials can be used.

Next, a first characteristic of a thin film transistor according to thefirst aspect of the invention resides in that a photosensitive typeorganic resin film, particularly, a positive type photosensitive acrylicfilm is used above the first passivation film 108 which is an inorganic,insulating film as an interlayer insulating film 109. A film thicknessof the photosensitive organic resin film 109 may be selected in a rangeof 1 through 4 μm (preferably, 1.5 through 3 μm). Further, a secondcharacteristic thereof resides in that a first opening portion(designated by diameter φ1) 110 is provided at the photosensitiveorganic resin film 109 and a second passivation film 111 which is aninorganic insulating film is provided to cover an upper face of thephotosensitive organic resin film 109 and an inner wall face of thefirst opening portion 110. Further, a third characteristic thereofreside in that the second passivation film 111 includes a second openingportion (designated by diameter φ2) 112 at a bottom face of the firstopening portion 110 and opening portions are formed also at the firstpassivation film 108 and the gate insulating film 106 with a diameterthe same as that of the second opening portion 112. That is, thecharacteristic resides in that the second opening portion provided at alaminated layer body including the gate insulating film 106, the firstpassivation film 108 and the second passivation film 111 is provided onan inner side of the first opening portion 110. Further, a sourceelectrode 113 is connected to the source region 103 via the firstopening portion 110 and the second opening portion 112 and a drainelectrode 114 is similarly connected to the drain region 104.

Further, as the first passivation film 108 and the second passivationfilm 111, the silicon nitride film, a silicon nitrooxide film, a siliconoxynitride film, an aluminum nitride film, an aluminum nitrooxide filmor an aluminum oxynitride film can be used. Further, a laminated layerfilm including these films at at least a portion thereof may beconstituted. Further, the diameter φ1 may be 2 through 10 μm(preferably, 3 through 5 μm) and the diameter φ2 may be 1 through 5 μm(preferably, 2 through 3 μm). However, the diameters need not torestrict to the numeral value ranges since the design rule of thediameters of the opening portions are changed also by accuracy ofphotolithography steps. That is, at any rate, a relationship of φ1>φ2may be satisfied.

Here, FIG. 3B shows a view enlarging a portion of a region 115surrounded by dotted lines. FIG. 3B shows portions of the first openingportion 110 and the second opening portion 112. The first openingportion 110 is formed with a gradual curved face at an inner wall facethereof and is provided with a radius of curvature which is continuouslychanged. For example, when attention is paid to radii of curvature R1,R2 and R3 successively, a relationship of the respective radii ofcurvature becomes R1<R2<R3 and numerical values thereof fall in a rangeof 3 through 30 μm (representatively, 10 through 15 μm). Further, at abottom face of the first opening portion 110, an angle made by thephotosensitive organic resin film 109 and the first passivation film 108(contact angle θ) falls in a range of 30°<θ<65° (representatively,40°<θ<50°).

In this case, in FIG. 3B, a portion designated by notation 116constitutes a state in which the first passivation film 108 and thesecond passivation film 110 are brought into close contact with eachother to seal the photosensitive organic resin film 109. In this case, alength of the close contact region, that is, a region of bringing thefirst passivation film 108 and the second passivation film 111 intocontact with each other may be 0.3 through 3 μm (preferably, 1 through 2μm), specifically, a radius of the first opening portion 110 may belarger than a radius of the second opening portion 112 by 0.3 through 3μm.

The photosensitive organic resin film (here, positive typephotosensitive acrylic film) used in the first aspect of the inventionmay generate a gas component in forming and after forming a thin filmtransistor and therefore, it is very important in the significance ofpreventing a deterioration in a liquid crystal element or an EL elementformed above the thin film transistor to seal the photosensitive organicresin film by inorganic insulating films having excellent close contactperformance (particularly, silicon nitride film or a silicon nitrooxidefilm having high barrier performance is preferable).

Further, it seems that when the contact angle (θ) shown in FIG. 3B isreduced, an inclination of an inner wall face of the first openingportion 110 becomes gradual and therefore, in FIG. 3A, a distancebetween an upper end portion (corner) of the gate electrode 107 and theinner wall face of the first opening portion 110 is shortened, however,three layers of insulating films of the first passivation film 108, thephotosensitive organic resin film 109 and the second passivation film111 are actually present between the gate electrode 107 and the wiring113 and therefore, a problem of shortcircuit or the like cannot beposed.

Next, a method of fabricating the thin film transistor having thestructure shown in FIGS. 3A and 3B will be explained in reference toFIGS. 4A, 4B, 4C, 4D and 4E. First, FIG. 4A will be explained. The basefilm 102 is formed above the substrate 101 and a semiconductor filmetched in an island-like shape is formed thereabove. Further, the gateinsulating film 106 is formed and the gate electrode 107 is formedthereabove and the source region 103 and the drain region 104 are formedself-adjustingly by using the gate electrode 107 as a mask. At thisoccasion, the channel forming region 105 is partitioned simultaneously.When the source region 103 and the drain region 104 are formed, thesource region 103 and the drain region 104 are activated by a heatingtreatment, the first passivation film 108 is formed and thereafter, ahydrogenating treatment is carried out by a heating treatment. Thefabricating method heretofore may be carried out by using a public-knowntechnology and as materials constituting the thin film transistor, allof publicly-known materials can be used. Next, as the interlayerinsulating film 109, a photosensitive organic resin film, in this case,a positive type photosensitive acrylic film is formed.

Next, FIG. 4B will be explained. When the photosensitive organic resinfilm 109 is formed, an exposing treatment by a photolithography step iscarried out and the photosensitive organic resin film 109 is etched tothereby form the first opening portion 110. The step is a technologyenabled by the photosensitive organic resin film, further, the etchingper se is wet etching by a developing solution and therefore, an effectthat the above-described problem of plasma damage is not posed isachieved. After etching by the developing solution, a decoloringtreatment of the photosensitive organic resin film 109 is carried out.The decoloring treatment may be carried out by irradiating lightstronger than light used in exposing to a total of a pattern. Further,the decoloring treatment needs to carry out immediately after exposing,that is, before a curing treatment. Because after curing, bridging ofthe photosensitive organic resin film 109 is finished and therefore,decoloring by irradiating light cannot be carried out.

Further, a sectional shape of the first opening portion 110 becomes asshown by FIG. 3B and includes a very gradual inner wall face. Therefore,coverage of an electrode to be formed later becomes extremely excellent.Further, in the curing step after etching, in order to preventadsorption or absorption of moisture or oxygen into the resin, it ispreferable to heat in an inactive atmosphere (nitrogen atmosphere, raregas atmosphere or hydrogen atmosphere). At this occasion, byconstituting the inactive atmosphere completely from elevatingtemperature to lowering temperature, an amount of adsorbing (orabsorbing) moisture and oxygen is preferably retrained to be equal to orsmaller than 10 ppm (preferably, equal to or smaller than 1 ppm).

Next, FIG. 4C will be explained. When the first opening portion 110 isformed, the second passivation film 111 is formed to cover an upper faceof the photosensitive organic resin film 109 and an inner wall face ofthe first opening portion 110. A material of the second passivation film111 may be the same as that of the first passivation film 108. Informing the second passivation film 111, a sputtering method by highfrequency discharge is preferably used. As conditions therefor, asilicon target may be used and nitrogen gas may be used as sputteringgas. Although the pressure may pertinently be set, the pressure may beset to 0.5 through 1.0 Pa, discharge power may be set to 2.5 through 3.5KW and film forming temperature may fall in a range from roomtemperature (25° C.) to 250° C. Further, when the second passivationfilm 111 is formed, a photoresist 201 is formed. The photoresist 201 isa mask for forming the second opening portion 112 to the secondpassivation film 111.

Next, FIG. 4D will be explained. When the photoresist 201 is formed, thesecond passivation film 111, the first passivation film 108 and the gateinsulating film 106 are successively etched by carrying out an etchingtreatment to thereby form the second opening portion 112. At thisoccasion, although the etching treatment may be a dry etching treatmentor a wet etching treatment, in order to improve the shape of the secondopening portion 112, the dry etching treatment is preferable. Accordingto the invention, even when the dry etching treatment is carried outhere, the photosensitive organic resin film 109 is not directly exposedto plasma. One of the characteristics of the first aspect of theinvention may reside in that while protecting the inner wall face of theopening portion provided at the photosensitive organic resin film by aninsulating nitride film of a silicon nitride film or the like, theopening portion having a smaller diameter is provided at the bottom faceof the opening portion in this way.

Further, in forming the second opening portion 112 by the dry etchingtreatment, the gate insulating film 106 and the first passivation film108 are etched and productivity of the etching can be promoted by acombination of inorganic insulating films. That is, when a siliconnitride film is used as the first passivation film 108 and a siliconoxynitride film is used as the gate insulating film 106, in etching thefirst passivation film 108, the gate insulating film 106 can be made tofunction as an etching stopper and in etching the gate insulating film106, the source region (silicon film) 103 can be made to function as anetching stopper.

For example, consider a case in which a silicon oxynitride film is usedfor the gate insulating film 106 and a silicon nitride film is used forthe first passivation film 108. Although the silicon nitride filmfunctioning as the first passivation film 108 can be etched by usingcarbon tetrafluoride (CF₄) gas, helium (He) gas and oxygen (O₂) gas,these gases also etch the silicon film. However, the silicon oxynitridefilm functioning as the gate insulating film 106 of the matrix isoperated as the etching stopper and therefore, the silicon filmfunctioning as the source region 103 is not eliminated. Further, thegate insulating film (here, silicon oxynitride film) 106 can be etchedby using hydrocarbon trifluoride (CHF₃) gas, further, the silicon filmis hardly etched thereby and therefore, the source region 103 can bemade to function as the etching stopper.

Next, FIG. 4E will be explained. When the second opening portion 112 isformed, a metal film is formed thereabove and patterned by etching tothereby form the source electrode 113 and the drain electrode 114. Inorder to form the electrodes, a titanium film, a titanium nitride film,a tungsten film (including alloy thereof), an aluminum film (includingalloy thereof) or a laminated layer film of these may be used.

The thin film transistor having the structure explained in reference toFIGS. 3A and 3B can be provided by carrying out the operation asdescribed above. The thin film transistor provided in this way includesthe photosensitive organic resin film and the photosensitive organicresin film functions also as a flattening film. Further, thephotosensitive organic resin film is sealed by the insulating nitridefilm (representatively, silicon nitride film or silicon nitrooxide film)and therefore, a problem by degassing is not posed.

An explanation will be given here of reason that the positive typephotosensitive acrylic film is particularly preferable as thephotosensitive organic resin film 109.

First, a photograph shown in FIG. 5A is a sectional SEM (scanningelectrode microscope) photograph of a state in which a nonphotosensitiveacrylic film (film thickness: about 1.3 μm) is subjected to a dryetching treatment to pattern and FIG. 5B is a schematic diagram thereof.When a nonphotosensitive acrylic film is subjected to a dry etchingtreatment as in a related art, a curved face is hardly formed at anupper portion of a pattern to constitute an upper end portion which isnot substantially provided with a radius of curvature (R). Further,although at a lower portion of the pattern, a taper angle (contactangle) is about 63° and a curved face is not observed also at the lowerend portion.

Next, a photograph shown in FIG. 7A is a sectional SEM photograph of astate in which a positive type photosensitive acrylic film (filmthickness: about 2.0 μm) is subjected to exposing and developingtreatments to pattern and FIG. 7B is a schematic diagram thereof. Asectional shape of the positive type photosensitive acrylic film isprovided with a very gradual curved face after an etching treatment by adeveloping solution and a radius of curvature (R) is continuouslychanged. Further, also a contact angle is provided with a small value ofabout 32 through 33°. That is, the shape is the shape shown by FIG. 3Bas it is and can be said to be very useful shape in fabricating a thinfilm transistor and a display device of the invention. Naturally, thevalue of the contact angle is changed by an etching condition or a filmthickness, however, 30°<θ<65° may be satisfied as mentioned above.

Next, a photograph shown in FIG. 8A is a sectional SEM photograph of astate in which a negative type photosensitive acrylic film (filmthickness: about 1.4 μm) is subjected to exposing and developingtreatments to pattern and FIG. 8B is a schematic diagram thereof. Asectional shape of the negative type photosensitive acrylic film isformed with a gradual curved face in an S-like shape after an etchingtreatment by a developing solution and is curved by a certain radius ofcurvature (R) at an upper end portion of the pattern. Further, thecontact angle is provided with a value of about 47°. In this case, alength of a portion of tail (skirt) designated by notation W of FIG. 8Bposes a problem. Particularly, at a contact hole (opening portion) whichneeds fine machining, when the tail portion is prolonged, there is aconcern of bringing about a situation in which an electrode or a wiringat a lower layer is not exposed at inside of the contact hole and thereis a concern of disconnection by contact failure. However, when thelength (W) of the tail portion is equal to or smaller than 1 μm(preferably, length less than a radius of the contact hole), such apossibility of disconnection is reduced.

Next, a photograph shown in FIG. 9A is a sectional SEM photograph of astate in which a positive type photosensitive polyimide film (filmthickness: about 1.5 μm) is subjected to exposing and developingtreatments and FIG. 9B is a schematic diagram thereof. Although asectional shape of the positive type photosensitive polyimide film isprovided with more or less of a tail portion (designated by a length W)and a curved upper end portion after an etching treatment by adeveloping solution, a radius of curvature (R) thereof is small.

When the above-described sectional shapes are observed, the followinganalysis can be carried out. When a metal film for constituting anelectrode or a wiring is formed after forming a contact hole (openingportion), a sputtering method, a vapor deposition method or a CVD methodis used. When molecules of a material for constituting a thin film areadhered to a face to be formed, the molecules are moved on a surfacewhile seeking for a stable site and it is known that the molecules areliable to gather to a portion of a shape having an acute angle as in anupper end portion of a contact hole (shape for constituting a projectedportion). The tendency is remarkable particularly in a vapor depositionmethod. Therefore, when the sectional shape of the opening portion isthe shape as shown by FIG. 5A, the molecules of the material areconcentrated on an edge of the opening portion and therefore, the filmthick thickness is increased locally only at the portion to form aprojected portion in an eaves-like shape. The projected portion causes afailure of disconnection (bench cut) or the like and therefore, is notpreferably. Therefore, the nonphotosensitive acrylic film shown in FIG.5A and the positive type photosensitive polyimide film shown in FIG. 9Acan be said to be disadvantageous materials in view of the coverage.

Further, with regard to the shape formed with the tail portion at thelower end portion of the contact hole as in FIG. 8A and FIG. 9A, thetail portion covers a bottom face of the contact hole depending oncases, there is a concern of bringing about contact failure andtherefore, the materials can be said to be disadvantageous materials inview of contact performance. Naturally, when a length of the tailportion is equal to or smaller than 1 μm (preferably, length less thanthe radius of the contact hole), no problem is posed.

From the above-described point, in embodying the invention, the positivetype photosensitive acrylic film constituting the shape shown in FIG. 7Acan be said to be most preferable. That is, when the positive typephotosensitive acrylic film is used, the very gradual curved face isprovided at the upper end portion of the contact hole and therefore, noproblem is posed in the coverage, further, at the lower end portion ofthe contact hole, the bottom face of the contact hole is firmlypartitioned by the contact angle satisfying 30°<θ<65° without formingthe tail portion and therefore, the problem of contact failure is notalso posed. From the above-described reason, in embodying the invention,the applicant considers, that the positive type photosensitive acrylicfilm is the most preferable material as an interlayer insulating filmcomprising an organic resin.

As described above, in fabricating the thin film transistor using theorganic resin film as the interlayer insulating film, the photosensitiveorganic resin film is used as the interlayer insulating film, further,by constituting the contact structure as shown by FIG. 3B, the thin filmtransistor can be fabricated without dispersing threshold voltage andpromotion of stability of operational function of not only the thin filmtransistor but also the display device using the thin film transistorand enlargement of design margin in circuit design can be achieved.

Further, an explanation will be given in reference to FIGS. 1A, 1B, 1Cand 1D. FIGS. 1A, 1B, 1C and 1D show a light emitting device(specifically, EL display device) fabricated by a fabricating processpreferable in embodying the first aspect of the invention.

In FIGS. 1A, 1B, 1C and 1D, FIG. 1A is a top view of a pixel of a lightemitting device (however, up to forming a pixel electrode), FIG. 1B is acircuit diagram thereof and FIGS. 1C and 1D are sectional viewsrespectively taken along a line A-A′ and a line B-B′ of FIG. 1A.

As shown by FIGS. 1A and 1B, a display portion of the light emittingdevice is provided with a plurality of pixels surrounded by a gatewiring 951, a data wiring 952 and a power source wiring (wiringsupplying constant voltage or constant current) 953 in matrixarrangement and each of the pixels is provided with TFT functioning as aswitching element (hereinafter, referred to as switching TFT) 954, TFTfunctioning as means for supplying current or voltage for making an ELelement emit light (hereinafter, referred to as driving TFT) 955, acapacitor portion 956 and an EL element 957. The EL element 957 can beformed by providing an EL layer on an upper side of a pixel electrode958, although not illustrated here.

Further, although in the embodiment, as the switching TFT 954, ann-channel type TFT of a multigate structure is used and as the drivingTFT 955, a p-channel type TFT is used, the pixel constitution of thelight emitting device needs not to limit thereto but can be embodied forall of publicly-known constitutions.

The sectional view of FIG. 1C shows the n-channel type TFT 954 and thecapacitor portion 956. Notation 900 designates a substrate and a glasssubstrate, a ceramic substrate, a quartz substrate, a silicon substrateor a plastic substrate (including plastic film) can be used therefor.Further, notation 901 designates a silicon nitrooxide film as a firstbase film and notation 902 designates a silicon oxynitride film as asecond base film. Naturally, the films need not to limit to thesematerials. Further, the first base film 901 and the second base film 902may be formed at layers on a lower side of an activation layer providedto a thin film transistor and therefore, need not to be provided atlayers on a lower side of the pixel electrode. The first base film orthe second base film may be formed at a layer on an upper side of thepixel electrode and an upper side of a pixel portion may be opened byincluding the base film.

The pixel electrode 958 formed by patterning a conductive oxide film ispreviously formed above the second base film 902. The point is the mostimportant characteristic. By previously providing the pixel electrode958 before forming a thin film transistor (that is, provided at a layeron a lower side of the activation layer), there is not posed a problemof damage inflicted on the thin film transistor in polishing to flattenthe pixel electrode which becomes problematic when the pixel electrodeis provided at a layer on an upper side of the thin film transistor asin an ordinary case and therefore, promotion of stability of operationalfunction of the thin film transistor can be achieved. Further, sinceonly the base film 1 and the base film 2 are present at layers on alower side of the pixel electrode, the polishing can be carried out in aflatter state. Further, although as the pixel electrode 958, aconductive oxide film (representatively, ITO film) transparent withrespect to visible light is used, the pixel electrode 958 does not needto limit thereto but may use other conductive oxide film. Further, thecharacteristic resides in that a silicon oxynitride film 903 is providedabove the pixel electrode 958 as a third base film and it is preferableto use an insulating film having a material the same as that of the gateinsulating film to be formed later or having a high selection ratio withthe activation layer. In such a significance, a silicon oxide film maybe used in place of the third base film 903.

As described above, the base film is constituted by a laminated layerbody of the first base film 901, the second base film 902 and the thirdbase film 903 and the pixel electrode 958 is provided in a state ofbeing covered by the base film constituting the laminated layer body(embedded state).

Further, the activation layer of the n-channel type TFT 954 is providedabove the silicon oxide film 903, the activation layer includes a sourceregion 904, a drain region 905, LDD regions 906 a through 906 d andchannel forming regions 907 a and 907 b, and the two channel formingregions and the four LDD regions are provided between the source region904 and the drain region 905. At this occasion, although thesemiconductor film constituting the activation layer can be formed by apublicly-known technology, it is preferable to form the semiconductorfilm in a temperature range which does not effect adverse influence onthe conductive oxide film previously formed. Representatively, it ispreferable to use a low temperature process of a laser crystallizingtechnology or a crystallizing technology using nickel.

Further, the activation layer of the n-channel type TFT 954 is coveredby a gate insulating film 908, and gate electrodes 909 a and 909 b andgate electrodes 910 a and 910 b are provided thereabove. Althoughaccording to the second aspect of the invention, a silicon oxynitridefilm is used for the gate insulating film 908, when an insulatingnitride film, mentioned above, of an aluminum nitride film having a highspecific inductive capacity is used, the insulating nitride film iseffective in increasing an integration degree since an occupied area ofthe element can be reduced.

Further, as the gate electrodes 909 a and 910 a, tantalum nitride filmsare used and as the gate electrodes 909 b and 910 b, tungsten films areused. The metal films are provided with high selection ratios with eachother and therefore, by selecting etching conditions, a structure asshown by FIG. 1B can be constituted. With regard to the etchingcondition, JP-A-2001-313397 by the applicant may be referred to.

Further, as a first passivation film 911 covering the gate electrodes, asilicon nitride film or a silicon nitrooxide film is provided and aphotosensitive organic resin film 912 (a positive type photosensitiveacrylic film is used according to the second aspect of the invention) isprovided thereabove. Further, the photosensitive organic resin film 911is provided with a second passivation film 913 to cover a first openingportion (refer to FIG. 1C) and a second opening portion (refer to FIG.1C) is provided at a bottom face of the first opening portion. Accordingto the second aspect of the invention, as the second passivation film913, a silicon nitride film or a silicon nitrooxide film is used.Naturally, other insulating nitride film of an aluminum nitride film oran aluminum nitrooxide film can also be used.

Further, the data wiring 952 is connected to the source region 904 viathe first opening portion and a connecting wiring 915 is connected tothe drain region 905 via the second opening portion. The connectingwiring 915 is a wiring connected to the gate of the driving TFT 954. Asthe data wiring 952 and the connecting wiring 915, a structure ofinterposing a wiring whose major component is a metal having lowresistance of aluminum or copper by other metal films or a film of analloy of these metals may be used.

Further, notation 916 designates a source region of the driving TFT 955connected with the power source wiring 953. A contact portion related tothe connection is formed with the first opening portion and the secondopening portion by embodying the first aspect of the invention. Further,the power source wiring 953 is opposed to a gate wiring 917 of thedriving TFT 955 via the first passivation film 911 and the secondpassivation film 913 and forms a storage capacitor 956 a. Further, thegate wiring 917 is opposed to a semiconductor film 918 via the gateinsulating film 908 and forms a storage capacitor 956 b. Since the powersource wiring 953 is connected to a semiconductor film 919, thesemiconductor film 918 functions as an electrode by being supplied withelectric charge therefrom. The capacitor portion 956 is constructed by aconstitution of connecting the storage capacitors 956 a and 956 b inparallel and therefore, large capacitance is provided by a very smallarea. Particularly, a silicon nitride film having a high specificinductive capacity as a dielectric body is used for the storagecapacitor 956 a and therefore, large capacitance can be ensured.Further, a dielectric body of the storage capacitor 956 a is constitutedby a laminated layer structure of the first passivation film 911 and thesecond passivation film 913 and therefore, a probability of producingpin holes is extremely low and a highly reliable capacitor can beformed.

When the first aspect of the invention is embodied, in comparison with arelated art, since the second opening portion is formed, the number ofmasks used in photolithography steps is increased, however, byconversely utilizing the increase in the number of masks, as shown bythe embodiment, the storage capacity can newly be formed. The point isalso one of significant characteristics of the first aspect of theinvention. The characteristic compensates for a disadvantage of theincrease in the masks, as a result, contributes significantly todevelopment of industry. For example, in order to achieve display ofhighly fine image, it is necessary to increase a numerical aperture byreducing an occupied area of a storage capacitor relative to an area ofeach pixel in a display portion and for such purpose, an increase in thestorage capacitor is extremely useful.

Further, in FIG. 1D, notation 920 designates a drain region of thedriving TFT 955 which is connected to a drain wiring 921. Further, thedrain region 921 is connected to the pixel electrode 958 via a firstopening portion 922 and a second opening portion 923 provided above thepixel electrode 958. At this occasion, when the second opening portion923 is formed, the second opening portion 923 is formed by etching thesecond passivation film 913, the first passivation film 911 and the gateinsulating film 908 and successively etching also the silicon oxide film903. That is, during a time period of etching the silicon oxide film903, it is necessary to prevent semiconductor films of the source region904, the drain region 905 and the drain region 920 from being etched.For that purpose, as described above, the silicon oxynitride film 903having a material the same as that of the gate insulating film 908 isselected.

FIGS. 2A and 2B show an example of actually forming an EL element in thelight emitting device having the above-described pixel constitution.Further, portions of FIGS. 2A and 2B the same as those of FIGS. 1A, 1B,1C and 1D are designated by numerals the same as those of FIGS. 1A, 1B,1C and 1D. FIG. 2A is a view in correspondence with a section shown byFIG. 1D, showing a state of forming an EL element 957 above the pixelelectrode 958. Further, when a structure of FIG. 2A is constituted, thepixel electrode 958 corresponds to an anode of the EL element 957.Further, in the specification, the EL element refers to an elementprovided with an EL layer between a cathode and an anode for emittinglight by applying voltage or injecting current to the EL layer.

The thin film transistor formed at an end portion of the pixel electrode958 and above the substrate is covered by a photosensitive organic resinfilm 961. It has a useful significance to protect the end portion of thepixel electrode 958 by the insulating film (first photosensitive organicresin film 912) since when the EL layer is provided at the end portionof the pixel electrode 958, shortcircuit between the anode and thecathode by bench cut poses a problem or there is a concern ofdeteriorating the EL layer by concentrating an electric field. Further,the photosensitive organic resin film 961 is provided in a lattice shapeto fringe the respective pixels or provided in a stripe shape by a unitof row or a unit of column. The light emitting device having thestructure of the invention is previously formed with the pixel electrode958 and therefore, provided with a function of protecting the endportion of the pixel electrode.

Further, according to the light emitting device having the structureshown in FIGS. 2A and 2B, as the photosensitive organic resin film(second photosensitive organic resin film) 961, a material the same asthat of the photosensitive organic resin film (first photosensitiveorganic resin film) 912 used as the interlayer insulating film (positivetype photosensitive acrylic film according to the second aspect of theinvention) is used and therefore, a production facility can beminimized. Further, although not illustrated, a negative typephotosensitive acrylic film constituting a sectional shape in an S-likeshape shown in FIGS. 8A and 8B may be used. Naturally, in this case, itis preferable to set radii of curvature at an upper end portion and alower end portion of an opening portion to 3 through 30 μm(representatively, 10 through 15 μm). Further, in that case, when thelength of the tail portion designated by notation W is not made as shortas possible, the numerical aperture is reduced, which is not preferable.Further, a publicly-known resist material (high molecular materialincluding chromofore) can be used.

Further, a surface of the photosensitive organic resin film 961 iscovered by an insulating nitride film as a third passivation film 962 tothereby enable to restrain degassing from the photosensitive organicresin film 961. Further, the third passivation film 962 is etched toprovide an opening portion above the pixel electrode 958 and an EL layer963 and the pixel electrode 958 are brought into contact with each otherat the opening portion. Although the EL layer 963 is generallyconstituted by laminating thin films of a luminescent layer, a chargeinjecting layer and a charge transporting layer, all of structures andmaterials confirming luminescence can be used. For example, SAlq(triphenylsilanol structure substitutes for one of three ligards ofAlq₃) constituting an organic material including silicon as an electrontransporting layer or a hole blocking layer can also be used.

Naturally, it is not necessary to constitute the EL layer 963 only byorganic thin films but may be constituted by a structure of laminatingan organic thin film and an inorganic thin film, or a polymeric thinfilm or a low molecular thin film. Further, although a method of formingthe film differs by using the high molecular thin film or using the lowmolecular thin film, the film may be formed by a publicly-known method.

Further, a cathode 964 is provided above the EL layer 963 and aninsulating nitride film as a fourth passivation film 965 is finallyprovided further thereabove. Although the cathode 964 may use a metalthin film including an element belonging to group I or group II of theperiodic table, a metal film of aluminum added with 0.2 through 1.5 wt %(preferably, 0.5 through 1.0 wt %) of lithium is preferable in view ofcharge injecting performance and the like. Further, although there is aconcern that the lithium is harmful for operation of TFT by beingdiffused, according to the embodiment, since the EL layer 963 iscompletely protected by the first passivation film 911, the secondpassivation film 913 and the third passivation film 962 and therefore,it is not necessary to be mindful of diffusion of lithium.

Here, FIGS. 17A and 17B show data indicating an effect of a siliconnitride film formed by a sputtering method by high frequency dischargeof blocking against lithium. FIG. 17A shows a C-V characteristic of anMOS structure constituting a dielectric body by a silicon nitride filmformed by a sputtering method by high frequency discharge (designated asRF-SP SiN). Further, notation “Li-dip” signifies that a solutionincluding lithium is subjected to spin coating above the silicon nitridefilm and signifies that the film is intentionally contaminated bylithium for the sake of test. The silicon nitride film formed by thesputtering method by high frequency discharge is formed by using acircular Si target having a radius of 12 inch under conditions of a gasflow rate ratio of N₂:Ar=20:20 (sccm), film forming gas pressure of 0.8Pa, film forming power of 3 kW in high frequency power and substratetemperature of 200° C. FIG. 20 and Table 1 show a result of measuring acomposition of the silicon nitride film formed by the sputtering methodby high frequency discharge by SIMS.

TABLE 1 H C O Ar Concentration (atoms/ 5 × 10²⁰ 4 × 10¹⁹ 2 × 10²¹ 3 ×10²⁰ cm³)

Further, FIG. 17B shows a C-V characteristic of an MOS structureconstituting a dielectric body by a silicon nitride film formed by aplasma CVD method for comparison (designated as CVD SiN). The siliconnitride film formed by the plasma CVD method is formed under conditionsof gas flow rates of SiH₄:NH₃:N₂:H₂=30:240:300:60 (sccm), pressure of159 Pa, frequency of 13.56 MHz, power of 0.35 W/cm² and substratetemperature of 325° C. Further, data of FIG. 17B uses a film of an alloyof aluminum added with lithium as a metal electrode. These films(silicon nitride film formed by sputtering method by high frequencydischarge, silicon nitride film formed by plasma CVD method) aresubjected to normal BT test (specifically, a heating treatment iscarried out for 1 hour at ±150° C. in addition to application of voltageof 1.7 MV), as a result, as shown by FIG. 17A, in comparison with thefact that a change is hardly observed in the C-V characteristic in thesilicon nitride film formed by the sputtering method by high frequencydischarge, a significant change is observed in the C-V characteristic inthe silicon nitride film formed by the plasma CVD method andcontamination by lithium is confirmed. The data indicates that thesilicon nitride film formed by the sputtering method by high frequencydischarge is provided with a very effective blocking effect againstdiffusion of lithium.

Further, a heat radiating effect can be expected by using the insulatingnitride film as the second passivation film 913 or the third passivationfilm 962. For example, when the heat conductivity of a silicon oxidefilm is set to 1, very high heat conductivities are provided for asilicon nitride film of about 5 and an aluminum nitride film of about 35through 130 and therefore, when the EL element is heated, the heat isradiated effectively and a deterioration of the EL layer 963 by selfheat generation can be restrained.

Further, the third passivation film 962 and the fourth passivation film965 can use a material the same as that of the insulating nitride filmused in the first passivation film 911 or the second passivation film913.

In the case of the structure shown in FIG. 2A, there is constituted alower emitting type in which light emitted from the EL element isemitted from a side of the substrate 901 by transmitting through thepixel electrode 958. In the case of the lower emitting type, since theinvention is provided with the structure in which the pixel electrode isprovided at the layer on the lower side of the activation layer of thethin film transistor and therefore, in comparison with a case in whichthe pixel electrode is provided at a layer on an upper side of the thinfilm transistor as in an ordinary case, the number of layers throughwhich light emitted from the EL layer transmits is small (lighttransmits only pixel electrode, base film 1, base film 2 and glasssubstrate) and therefore, the structure is advantageous in view oftransmittance of light.

Next, FIG. 2B shows an example of a metal film 971 having reflectingperformance in place of the pixel electrode 958 and as the metal film971 having the reflecting performance, a metal film having a high workfunction of platinum (Pt) or gold (Au) for functioning as an anode isused. Further, since the metals are expensive, there may be constituteda pixel electrode which is laminated above a pertinent conductive filmof an aluminum film, a tungsten film or a silicon film at least thetopmost surface of which is exposed with platinum or gold. Particularly,when a silicon film is used, the silicon film can be formedsimultaneously with the activation layer of the thin film transistor,which is preferable. Notation 972 designates an EL layer and all ofstructures and materials confirming luminescence can be used thereforsimilar to the case of FIG. 2A. Further, notation 973 designates a metalfilm having a thin film thickness (preferably, 10 through 50 nm) and ametal film including an element belonging to group I or group II of theperiodic table is used for functioning as a cathode. Further, aconductive oxide film (representatively, ITO film) 974 is provided tolaminate the metal film 973 and a fourth passivation film 975 isprovided thereabove.

In the case of the structure shown in FIG. 2B, light emitted from the ELelement is reflected by the pixel electrode 971 and emitted from thesubstrate by transmitting through the metal film 973 and the conductiveoxide film 974.

Although FIG. 2A shows the case in which light emitted from the ELelement is emitted from the substrate 901 by transmitting through thepixel electrode 958 (lower emitting type) and FIG. 2B shows the case inwhich light emitted from the EL element is reflected by the pixelelectrode 971 and emitted by transmitting through the metal film 973 andthe conductive oxide film 974 (upper emitting type), a structure inwhich light emitted from the EL element is emitted from both of an upperside and a lower side. In this case, a conductive oxide film havinglight transmitting performance (representatively, ITO film) maysubstitute for the metal film 971 having the reflecting performance ofFIG. 2B to form a pixel electrode. FIG. 19 shows an example of aspecific structure. In FIG. 19, notation 981 designates a pixelelectrode formed by a conductive oxide film of ITO film or the like,notation 982 designates an EL layer, and notation 983 designates a metalfilm having a thin film thickness (preferably, 10 through 50 nm). As themetal film 983, a metal film including an element belonging to group Ior group II of the periodic table is used for functioning as a cathode.Further, a conductive oxide film (representatively, ITO film) 984 isprovided to laminate the metal film 983 and a fourth passivation film985 is provided thereabove.

Further, means for resolving the second problem (hereinafter, referredto as second aspect of the invention) will be explained as follows inreference to FIGS. 21A, and 21B. The second aspect of the invention is alight emitting device (specifically, EL display device) fabricated bythe fabricating process preferable in embodying the first aspect of theinvention and is an aspect of the invention characterized in that thefabricating process is reduced by reducing the number of laminatedlayers as a whole and fabricating cost is reduced as a result.

According to the structure shown by FIGS. 2A and 2B, since the pixelelectrode is previously provided before forming the thin film transistorand therefore, it is not necessarily needed to provide a flattening filmwhich is necessary when the pixel electrode is provided at a layer on anupper side of the thin film transistor (in FIGS. 2A and 2B,photosensitive organic resin film 961) as in an ordinary case. FIGS. 21Aand 21B show a structure when the photosensitive organic resin film 961is not provided. FIG. 21A shows a case in which the photosensitiveorganic resin film 961 of FIG. 2A is not provided and FIG. 21A shows acase in which the photosensitive organic resin film 961 of FIG. 2B isnot provided. In FIG. 21A, notation 991 designates an insulating nitridefilm which is a third passivation film, notation 992 designates acathode, notation 993 designates an insulating nitride film which is afourth passivation film. FIG. 21A differs from FIG. 2A only in that thephotosensitive organic resin film is not provided. In FIG. 21B, notation994 designates an insulating nitride film which is a third passivationfilm, notation 995 designates a metal film having a thin film thickness(preferably, 10 through 50 nm), notation 996 designates a conductiveoxide film (representatively, ITO film), and notation 997 designates aninsulating nitride film which is a fourth passivation film. FIG. 21Bdiffers from FIG. 2B only in that the photosensitive organic resin filmis not provided. When the photosensitive organic resin film 961 is notprovided as in the above-described cases, the number of masks can bereduced by one sheet (mask for forming the photosensitive organic resinfilm 961). An advantage of capable of reducing the number of steps isachieved and the second problem of the invention can be resolved.Naturally, the above-described effect in the structure shown in FIGS. 2Aand 2B, that is, the effect by which there is not posed the problem ofdamage inflicted on the thin film transistor when the pixel electrode ispolished to flatten and the effect by which the polishing can be carriedout in the flatter state are also achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are views showing a pixel constitution of alight emitting device;

FIGS. 2A and 2B are views showing a sectional structure of the lightemitting device;

FIGS. 3A and 3B are views showing a structure of a thin film transistor;

FIGS. 4A, 4B, 4C, 4D and 4E are views showing steps of fabricating thethin film transistor;

FIGS. 5A and 5B are a SEM photograph and a schematic diagram showing asectional structure of an organic resin film;

FIGS. 6A and 6B are diagrams showing a dispersion of threshold voltage;

FIGS. 7A and 7B are a SEM photograph and a schematic diagram showing asectional structure of an organic resin film;

FIGS. 8A and 8B are a SEM photograph and a schematic diagram showing asectional structure of an organic resin film;

FIGS. 9A and 9B are a SEM photograph and a schematic diagram showing asectional structure of an organic resin film;

FIGS. 10A and 10B are diagrams showing a structure of a thin filmtransistor;

FIG. 11 is a diagram showing a structure of a thin film transistor;

FIGS. 12A, 12B, 12C and 12D are diagrams showing a pixel constitution ofa liquid crystal display device;

FIGS. 13A and 13B are views showing a sectional structure of a liquidcrystal display device;

FIGS. 14A, 14B, 14C and 14D are views showing an outlook constitution ofa light emitting device;

FIG. 15 is a diagram showing an outlook constitution of a light emittingdevice;

FIGS. 16A, 16B, 16C, 16D, 16E, 16F, 16G and 16H are views showingspecific examples of electric apparatus;

FIGS. 17A and 17B are diagrams showing a C-V characteristic of an MOSstructure for making a silicon nitride film dielectric;

FIGS. 18A, 18B, 18C and 18D are views showing steps of fabricating athin film transistor and a storage capacitor;

FIG. 19 is a view showing a sectional structure of a light emittingdevice;

FIG. 20 shows an SIMS measurement data of a silicon nitride film;

FIGS. 21A and 21B are views showing a sectional structure of an lightemitting device; and

FIG. 22 is a view showing a sectional structure of a liquid crystaldisplay device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiment 1

According to the embodiment, an explanation will be given of an exampleof making a position of forming the first opening portion 110 in FIGS.3A and 3B differ therefrom in reference to FIGS. 10A and 10B. Further,FIGS. 10A and 10B show a sectional structure at a time point of forminga second opening portion. Further, notations used in FIGS. 3A and 3B arereferred as necessary.

In FIG. 10A, notation 801 designates a first opening portion having adiameter φ1 and notation 802 designates a second opening portion havinga diameter φ2. A characteristic of FIG. 10A resides in that the firstopening portion 801 is provided to extrude from an end portion of thesource region 103. The photosensitive organic resin film 109 can beformed at a position as shown by the embodiment since progress ofetching is stopped by constituting an etching stopper by the firstpassivation film 108. Further, the structure can be constitutedsimilarly not only at a portion in contact with the source region or thedrain region but also a portion in contact with the gate electrode 107.

Further, in FIG. 10B, notation 803 designates a first opening portionhaving a diameter φ3 and notation 804 designates a second openingportion having a diameter φ2. A characteristic of FIG. 10B also residesin that the first opening portion 803 is provided to extrude from a sideend portion of the source region 103. Also in this case, progress ofetching the photosensitive organic resin film 109 is stopped byconstituting the etching stopper by the first passivation film 108.Further, the contact structure can be constituted similarly not only ata portion in contact with the source region or the drain region but alsoat a portion in contact with the gate electrode 107.

As described above, since there is present an inorganic insulating filmwhich can constitute the etching stopper under the photosensitiveorganic resin film used as the interlayer insulating film, even when thediameter of the first opening portion is increased, no problem is posed,which is very useful in view of the fact that design margin in forming acontact hole can be widened.

Embodiment 2

According to the embodiment, there is shown an example of using a bottomgate type thin film transistor (specifically, inverse stagger type TFT)as a thin film transistor in embodying the first aspect of the inventionor the second aspect of the invention, that is, an example of using aninverse stagger type TFT as a switching TFT and a driving TFT inembodying the light emitting device shown in FIGS. 1A and 1B.

The embodiment will be explained in reference to FIG. 11. In FIG. 11A,notation 301 designates a substrate, notation 302 designates a gateelectrode, notation 303 designates a gate insulating film, notation 304designates a source region, notation 305 designates a drain region,notations 306 a and 306 b designate LDD regions, notation 307 designatesa channel forming region and these are constituted by using asemiconductor film provided above the gate insulating film provided tocover the gate electrode 302. Further, notations 308 and 309 designateinorganic insulating films and according to the embodiment, notation 308designates a silicon oxide film and notation 309 designates a siliconnitride film. The silicon nitride film 309 functions as a firstpassivation film and the silicon oxide film 308 functions as a bufferlayer between the semiconductor layer constituting a lower layer and thefirst passivation film 309 comprising silicon nitride. Heretofore, thereis shown a structure of a publicly-known thin film transistor and all ofpublicly-known materials can be used for materials of respectiveportions thereof.

Next, above the first passivation film 309, as an interlayer insulatingfilm 310, a photosensitive organic resin film, specifically, a positivetype photosensitive acrylic film is provided and the photosensitiveorganic resin film 310 is provided with a first opening portion(designated by diameter φ1) 311. Further, a second passivation film 312comprising an inorganic insulating film is provided to cover an upperface of the photosensitive organic resin film 310 and an inner wall faceof the first opening portion 311 and the second passivation film 312 isprovided with a second opening portion (designated by diameter φ2) 313at a bottom face of the first opening portion 311. Further, notation 314designates a source electrode and notation 315 designates a drainelectrode.

Also in the embodiment, similar to the thin film transistor of FIG. 3Aand FIG. 3B, as the first passivation film 309 and the secondpassivation film 312, a silicon nitride film, a silicon nitrooxide film,a silicon oxynitride film, an aluminum nitride film, an aluminumnitrooxide film or an aluminum oxynitride film can be used. Further, alaminated film including at least portions of the films can beconstituted. Further, the diameter φ1 may be 2 through 10 μm(preferably, 3 through 5 μm), the diameter φ2 may be 1 through 5 μm(preferably, 2 through 3 μm) and a relationship of φ1>φ2 may besatisfied. Further, although an explanation of the sectional shape ofthe first opening portion 311 will be omitted here since a detailedexplanation thereof is given in the summary of the invention, it ispreferable that the inner wall face constitutes a smooth curved face andis provided with a radius of curvature continuously changed.Specifically, when an attention is paid to radii of curvature R1, R2, R3at three points successively, it is preferable that a relationship amongthe radii of curvature becomes R1<R2<R3 and numerical values thereof are3 through 30 μm (representatively, 10 through 15 μm). Further, at thebottom face of the first opening portion 311, an angle made by thephotosensitive organic resin film 310 and the first passivation film 309(contact angle θ) preferably falls in a range of 30°<θ<65°(representatively, 40°<θ<50°).

As described above, in embodying the first aspect of the invention orthe second aspect of the invention, it is not necessary to limit astructure of the thin film transistor only to the top gate type or onlyto the bottom gate type and the invention is applicable to allstructures of thin film transistors. Further, the invention is notlimited to thin film transistors but is applicable to a transistor of anMOS structure fabricated by forming a well on a silicon wafer.

Embodiment 3

According to the embodiment, an explanation will be given of an examplein which the first aspect of the invention or the second aspect of theinvention is applied to a liquid crystal display device. In FIGS. 12A,12B, 12C and 12D, FIG. 12A is a top view at a pixel of a liquid crystaldisplay device (however, up to forming a pixel electrode), FIG. 12B is acircuit diagram thereof and FIGS. 12C and 12D are sectional views takenalong a line A-A′ and a line B-B′ of FIG. 12A.

As shown by FIGS. 12A and 12B, a display portion of the liquid crystaldisplay device includes a plurality of pixels surrounded by gate wiring851 and a data wiring 852 in a matrix arrangement and each of the pixelsis provided with TFT functioning as a switching element (hereinafter,referred to as switching TFT) 853, a capacitor portion 854 and a liquidcrystal element 855. Further, although the liquid crystal element 855 isnot illustrated in FIG. 2A, the liquid crystal element 855 can be formedby providing a liquid crystal layer above a pixel electrode 857.Although in the circuit diagram shown by FIG. 12B, both of the capacitorportion 854 and the liquid crystal element 855 are connected to aconstant potential line 856, it is not necessary to maintain the both atthe same potential but one of them may be maintained at common potentialand other thereof may be maintained at ground potential. Further,although according to the embodiment, an n-channel type TFT having amultigate structure is used as the switching TFT 853, a p-channel typeTFT may be used therefor. Further, layout of switching TFT maypertinently be set by a person of embodying the invention.

The switching TFT 853 and the capacitor portion 854 are shown in thesectional diagram of FIG. 12C. Notation 800 designates a substrate and aglass substrate, a ceramic substrate, a quartz substrate, a siliconsubstrate or a plastic substrate (including plastic film) can be usedtherefor. Further, notation 801 designates a silicon nitrooxide film andnotation 802 designates a silicon oxynitride film which are laminated tofunction as a base film. Naturally, it is not necessary to limit thefilms to these materials.

The pixel electrode 857 formed by patterning an oxide conductive film ispreviously formed above the silicon oxynitride film 802. That is, bypreviously providing the pixel electrode 857 before forming a thin filmtransistor, the number of the laminated layers of a total of the circuitcan be reduced. Further, although an oxide conductive film which istransparent with respect to visible light (representatively, ITO film)is used as the pixel electrode 857, the film is not limited thereto butother oxide conductive film may be used. Further, a silicon oxynitridefilm 803 is provided above the pixel electrode 857. It is preferablethat an insulating film having a material the same as that of a gateinsulating film formed later or having a high selection ratio with anactivation layer is used similar to the case of second aspect of theinvention.

Further, an activation layer of the switching TFT 853 is provided abovethe silicon oxynitride film 803 and the activation layer includes asource region 804, a drain region 805, LDD regions 806 a through 806 dand channel forming regions 807 a and 807 b, and the two channel formingregions and the four formed LDD regions are provided between the sourceregion 804 and the drain region 805.

Further, the activation layer of the switching TFT 853 is covered by agate insulating film 808, and gate electrodes 809 a and 809 b and gateelectrodes 810 a and 810 b are provided thereabove. Further, as the gateelectrodes 809 a and 810 a, tantalum nitride films are used and as thegate electrodes 809 b and 810 b, tungsten films are used. The metalfilms are provided with high selection ratios with each other andtherefore, a structure as shown by FIG. 12B can be constituted byselecting etching conditions. With regard to the etching conditions,JP-A-2001-313397 by the applicant may be referred to.

Further, as a first passivation film 811 covering the gate electrodes, asilicon nitride film or a silicon nitrooxide film is provided and aphotosensitive organic resin film 812 (according to the embodiment, apositive type photosensitive acrylic film is used) is providedthereabove. Further, the photosensitive organic resin film 812 isprovided with a second passivation film 813 to cover a first openingportion (refer to FIG. 3B) and a second opening portion (refer to FIG.3B) is provided at a bottom face of the first opening portion. Accordingto the embodiment, as the second passivation film 813, a silicon nitridefilm or a silicon nitrooxide film is used. Naturally, other insulatingnitride film of an aluminum nitride film or an aluminum nitrooxide filmcan also be used.

Further, the data wiring 852 is connected to the source region 804 viathe first opening portion and the drain wiring 815 is connected to thedrain region 805 via the second opening portion. The drain wiring 815 isused as an electrode constituting a storage capacitor at the capacitorportion and electrically connected to the pixel electrode 857. Further,although according to the embodiment, an oxide conductive film which istransparent with respect to visible light (representatively, ITO film)is used as the pixel electrode 857, the invention is not limitedthereto. Further, the data wiring 852 and the drain wiring 815 may use astructure interposing a wiring whose major component is a metal havinglow resistance of aluminum or copper by other metal films or an alloyfilm of these metals.

The drain wiring 815 is opposed to a capacitor wiring 816 formedsimultaneously with the gate electrode (that is, formed at a face thesame as that of the gate electrode) via the first passivation film 811and the second passivation film 813 and forms a storage capacitor 854 a.Further, the capacitor wiring 816 is opposed to a semiconductor film 817via the gate insulating film 808 and forms a storage capacitor 854 b.The semiconductor film 817 is electrically connected to the drain region805 and therefore, functions as electrode by applying constant voltageto the capacitor wiring 816 in this way, the capacitor portion 854 isconstructed by a constitution connected in parallel with the storagecapacitors 854 a and 854 b and therefore, large capacitance is providedby a very small area. Further, particularly the storage capacitor 854 acan ensure large capacitance since the silicon nitride film having ahigh specific inductive capacity is used as a dielectric body.

FIGS. 13A and 13B show an example of actually forming up to a liquidcrystal element in the liquid crystal display device having theabove-described pixel constitution. FIG. 13A is a view in correspondencewith the section shown in FIG. 12C, showing a state of forming theliquid crystal element 855 above the pixel electrode 857. A spacer 821comprising an organic resin is provided above the drain wiring 815 andan alignment film 822 is provided from thereabove. An order of formingthe spacer 821 and the alignment film 822 may be reversed. Further, alight blocking film 824 comprising a metal film, an opposed electrode825 comprising a conductive oxide film and an alignment film 826 areprovided on other substrate (opposed substrate) 823 and the alignmentfilm 822 and the alignment film 826 are pasted together to be opposed toeach other by using a seal member (not illustrated). Further, a liquidcrystal 827 is injected from a liquid crystal injection port provided atthe seal member and the liquid crystal injection port is sealed tothereby finish the liquid crystal display device. Further, general cellintegrating steps of liquid cell may be applied to steps after formingthe spacer 821 and therefore, a detailed explanation thereof will not begiven particularly.

Further, although as rubbing treatment of the alignment film 822,general rubbing treatment may be carried out, or rubbingless technologymay be used, when a diamond-like carbon (DLC) film is used as the thirdbase film 803 in FIG. 12C, in forming the second opening portion abovethe pixel electrode 857, only the DLC film can selectively made toremain and therefore, a technology of achieving alignment property canbe used by irradiating laser to the DLC film.

When the structure shown in FIG. 13A is constituted, light is incidenton the side of the opposed substrate 823, modulated by the liquidcrystal 827 and emitted from the side of the substrate 801. At thisoccasion, transmitting light transmits through the photosensitiveorganic resin film 812 used for the interlayer insulating film andtherefore, it is necessary to make the photosensitive organic resin film812 sufficiently transparent by sufficiently carrying out decoloringtreatment.

Further, when the structure shown in FIG. 13A is constituted, thestructure is useful in that a height of the spacer 821 needs not to beheightened more than necessary. That is, although when a normal TNliquid crystal is used, a cell gap is around 0.4 μm and in that case,also the height of the spacer needs to be around 4 μm, when thestructure of the embodiment is constituted, the cell gap is constitutedby a height constituted by adding the height of the spacer to a heightderived from the thin film transistor (about 1.5 through 2 μm).Therefore, the height of the spacer 821 per se is sufficiently about 2.0through 2.5 μm, which is a range capable of being formed by coating by asufficiently uniform film thickness. Further, even when lighttransmitting through the display region (region occupied by the pixelelectrode 857) is scattered to the side of the thin film transistor, asis apparent from FIGS. 12A and 12B and FIG. 13A, the drain wiring 815 isprovided to cover a wall face of the photosensitive organic resin film812 and therefore, an advantage of functioning as the light blockingfilm to scattering of light from a horizontal direction is achieved.Further, a distance for light transmitting through the display region ofthe pixel to transmit through the insulating film is shortened andtherefore, optical loss by scattering at an interface can be restrained.

Next, FIG. 13B shows an example of utilizing a drain wiring 831comprising a metal film having a reflecting property as it is in placeof the pixel electrode 857 and as the metal film having the reflectingproperty, an aluminum film (including aluminum alloy film) or aconductive film having at least a silver thin film at a surface thereofcan be used. An explanation of other portions attached with notationsthe same as those of FIG. 13A will be omitted. When the structure shownby FIG. 13B is constituted, light is incident on the side of the opposedsubstrate 823, modulated by the liquid crystal 827 and emitted againfrom the side of the opposed substrate 823. Also in this case, an effectsimilar to that in the case of FIG. 13A is achieved.

Further, by thickly forming the photosensitive organic resin film asshown by FIG. 22, a structure serving also as a spacer can beconstituted. In FIG. 22, notation 841 designates a photosensitiveorganic resin film formed to serve also as a spacer. In the case of thestructure as shown by FIG. 22, it is not necessary to provide the spacer821 as shown by FIGS. 13A and 13B and therefore, the number of masks canbe reduced by one sheet (a mask for forming a spacer), further, a stepof forming the spacer can be omitted. Further, since FIG. 22 shows thestructure serving also as the spacer by thickly forming thephotosensitive organic resin film in FIG. 13A, other than thephotosensitive organic resin film and the spacer is constituted bysimilar structure and therefore, portions the same as those of FIG. 13Aare designated by the same numerals.

Embodiment 4

In this embodiment, a structure of the entire light emitting deviceshown in FIGS. 1A to 1D will be described using FIGS. 14A to 14D. FIG.14A is a plan view of a light emitting device produced by sealing anelement substrate in which thin film transistors are formed with asealing material. FIG. 14B is a cross sectional view along a line B-B′in FIG. 14A. FIG. 14C is a cross sectional view along a line A-A′ inFIG. 14A.

A pixel portion (display portion) 402, a data line driver circuit 403,gate line driver circuits 404 a and 404 b, and a protective circuit 405,which are provided to surround the pixel portion 402, are located on asubstrate 401, and a seal material 406 is provided to surround them. Thestructure of the pixel portion 402 preferably refers to FIGS. 1A-D andits description. As the seal material 406, a glass material, a metallicmaterial (typically, a stainless material), a ceramic material, or aplastic material (including a plastic film) can be used. As shown inFIGS. 1A-D, it can be also sealed with only an insulating film. Inaddition, it is necessary to use a transparent material according to aradiation direction of light from an EL element.

The seal material 406 may be provided to partially overlap with the dataline driver circuit 403, the gate line driver circuits 404 a and 404 b,and the protective circuit 405. A sealing material 407 is provided usingthe seal material 406, so that a closed space 408 is produced by thesubstrate 401, the seal material 406, and the sealing material 407. Ahygroscopic agent (barium oxide, calcium oxide, or the like) 409 isprovided in advance in a concave portion of the sealing material 407, sothat it has a function of absorbing moisture, oxygen, and the like tokeep an atmosphere clean in an inner portion of the above closed space408, thereby suppressing the deterioration of an EL layer. The concaveportion is covered with a cover material 410 with a fine mesh shape. Thecover material 410 allows air and moisture to pass therethrough but notthe hygroscopic agent 409. Note that the closed space 408 is preferablyfilled with a noble gas such as nitrogen or argon, and can be alsofilled with a resin or a liquid if it is inert.

Also, an input terminal portion 411 for transmitting signals to the dataline driver circuit 403 and the gate line driver circuits 404 a and 404b is provided on the substrate 401. Data signals such as video signalsare transferred to the input terminal portion 411 through a FPC(flexible printed circuit) 412. With respect to a cross section of theinput terminal portion 411, as shown in FIG. 14B, an input wiring havinga structure in which an oxide conductive film 414 is laminated on awiring 413 formed together with a gate wiring or a data wiring iselectrically connected with a wiring 415 provided in the FPC 412 sidethrough a resin 417 to which conductors 416 are dispersed. Note that aspherical polymer compound for which plating processing using gold orsilver is conducted is preferably used for the conductors 416.

Also, an enlarged view of a region 418 surrounded by a dot line in FIG.14C is shown in FIG. 14D. The protective circuit 405 is preferablycomposed by combining a thin film transistor 419 and a capacitor 420,and any known structure may be used therefor. The present invention hassuch a feature that the formation of the capacitor is possible withoutincreasing the number of photolithography steps together with theimprovement of contact holes. In this embodiment, the capacitor 420 isformed utilizing the feature. Note that the structure of the thin filmtransistor 419 and that of the capacitor 420 can be understood if FIGS.1A-D and description thereof are referred to, and therefore thedescription is omitted here.

In this embodiment, the protective circuit 405 is provided between theinput terminal portion 411 and the data line driver circuit 403. When anelectrostatic signal such as an unexpected pulse signal is inputtedtherebetween, the protective circuit releases the pulse signal to theoutside. At this time, first, a high voltage signal which isinstantaneously inputted can be dulled by the capacitor 420, and otherhigh voltages can be released to the outside through a circuit composedof a thin film transistor and a thin film diode. Of course, theprotective circuit may be provided in other locations, for example, alocation between the pixel portion 402 and the data line driver circuit403 or locations between the pixel portion 402 and the gate line drivercircuits 404 a and 404 b.

As described above, according to this embodiment, when the presentinvention is carried out, an example in which the capacitor used for theprotective circuit for electrostatic measures and the like which isprovided in the input terminal portion is simultaneously formed isindicated. This embodiment can be carried out by being combined with anystructure of Embodiments 1 and 2.

Embodiment 5

The embodiment shows an example of a light emitting device having aconstitution different from that of Embodiment 4. FIG. 15 is used forthe explanation. FIG. 15 is a sectional view in correspondence with FIG.14C, the pixel portion 402, the data line driving circuit 403 and theprotecting circuit 405 are provided above the substrate 401 and theinput terminal portion 411 is provided above an extended line of thecircuits. The pixel portion 402, the data line driving circuit 403 andthe protecting circuit 405 seal the El element by using a protectivefilm 421 similar to the light emitting device shown in FIGS. 1A, 1B, 1Cand 1D and is constituted very thinly.

Further, according to the embodiment, electric connection to an outsidedriving circuit is ensured by using TCP (tape carrier package) 422. TCP422 is constructed by a constitution provided with IC chips 422 a though422 d at a TAB (tape automated bonding) tape portion and adhered withTCP 422 in a direction of disposing the IC chips 422 a through 422 dabove the substrate 401. Therefore, a thickness of the light emittingdevice can be made to be very thin and by using the light emittingdevice at a display portion, an electric apparatus excellent inportability can be provided. Further, when a flexible substrate(representatively, plastic film) is used as a substrate, a flexiblelight emitting device is provided and therefore, a flexible electricapparatus capable of being pasted on a curved face can be realized.

Further, the constitution shown in the embodiment can freely be combinedwith the constitutions shown in any of FIGS. 1A, 1B, 1C, 1D and the 2Aand 2B and Embodiments 1 through 4.

Embodiment 6

According to the embodiment, an explanation will be given of an exampleof forming a thin film transistor and a storage capacitor connected tothe thin film transistor by a process different from that in FIGS. 4A,4B, 4C, 4D and 4E in reference to FIGS. 18A, 18B, 18C and 18D. First,FIG. 18A will be explained. A base film 202 is formed on a substrate 201and a semiconductor film etched in an island-like shape is formedthereabove. Further, a gate insulating film 207 is formed, a gateelectrode 208 and a capacitor electrode 209 are formed, and a sourceregion 203 and a drain region 204 are formed self-adjustingly by usingthe gate electrode 208 as a mask. At this occasion, a channel formingregion 205 and a semiconductor region 206 functioning as one electrodeof the storage capacitor are simultaneously partitioned. When the sourceregion 203 and the drain region 204 are formed, the source region 203and the drain region 204 are activated by a heating treatment, a firstpassivation film 210 is formed and thereafter, a hydrogenating treatmentis carried out by a heating treatment. A fabricating method heretoforemay be carried out by using a publicly-known technology and as materialsof constituting the thin film transistor, all of publicly-knownmaterials can be used.

Next, a protective film 211 is formed above the first passivation film210. A film thickness thereof may be selected in a range of 30 through70 nm (preferably 45 through 55 nm). As the protective film 211, asilicon oxide film or a silicon oxynitride film is used. Further, aphotosensitive organic resin film 213 (here, a positive typephotosensitive acrylic film) provided with a first opening portion 212is formed above the protective film 211. The photosensitive organicregion film 213 is photosensitive and therefore, patterning can becarried out by directly exposing the film to light and can be etched bydevelopment thereof. Naturally, after etching by an etching solution, adecoloring treatment and a curing treatment of the photosensitiveorganic resin film 213 are carried out. Further, with regard to thedecoloring treatment and the curing treatment, the explanation of FIGS.4A, 4B, 4C, 4D and 4E may be referred to.

Next, FIG. 18B will be explained. When the first opening portion 212 isformed, the exposed protective film 211 is etched with thephotosensitive organic resin film 213 as a mask. At this occasion, thefirst passivation film 210 functions as an etching stopper. Next, asecond passivation film 214 is formed to cover an upper face of thephotosensitive organic resin film 213 and an inner wall face of thefirst opening portion 212. The second passivation film 214 may beconstituted by a material the same as that of the first passivation film210. As described in the explanation of FIGS. 4A, 4B, 4C, 4D and 4E, itis preferable to form the second passivation film 210 by a sputteringmethod by high frequency wave discharge. At that occasion, as conditionstherefor, the explanation of FIGS. 4A, 4B, 4C, 4D and 4E may be referredto. Further, when the second passivation film 214 is formed, aphotoresist 215 is formed. The photoresist 215 is a mask for forming asecond opening portion at the second passivation film 214.

Next, FIG. 18C will be explained. When the photoresist 215 is formed,the second passivation film 214, the first passivation film 210 and thegate insulating film 207 are successively etched by carrying out anetching treatment to thereby form a second opening portion 216. At thisoccasion, although the etching treatment may be carried out by a dryetching treatment or a wet etching treatment, in order to improve theshape of the second opening portion 216, the dry etching treatment ispreferable. According to the invention, in forming the second openingportion 216, even when the dry etching treatment is carried out, thephotosensitive organic resin film 213 is not directly exposed to plasma.

Next, FIG. 18D will be explained. When the second opening portion 216 isformed, a metal film is formed thereabove and patterned by etching tothereby form a source electrode 217 and a drain electrode 218. In orderto form the electrodes, a titanium film, a titanium nitride film, atungsten film (including alloy thereof), an aluminum film (including anally thereof) or a laminated film of these may be used. Further, thedrain electrode 218 is extended to overlap the capacitor electrode 209.When such a structure is constituted, a first storage capacitor 219 a isformed by the semiconductor region 206, the gate insulating film 207 andthe capacitor electrode 209 and a second storage capacitor 219 b isconstituted by the capacitor electrode 209, the first passivation film210, the second passivation film 214 and the drain electrode 218.Therefore, since the first storage capacitor 219 a and the secondstorage capacitor 219 b can be provided in parallel, large capacitancevalue can be ensured by a small area. Since a dielectric body of thesecond storage capacitor 219 b is constituted by two layers of alaminated layer structure and therefore, a probability of producing pinholes is low and a highly reliable storage capacitor can be constituted.

As described above, the thin film transistor and the storage capacitorconnected to the thin film transistor having the structure shown in FIG.18D can be provided. Further, although according to the embodiment, anexplanation has been given by applying the invention to the thin filmtransistor having a simple structure, the embodiment is also applicableto thin film transistors of all of publicly-known structures and canfreely be combined with the constitutions of any of Embodiments 1through 5.

Embodiment 7

Examples of electronic apparatuses employing a display device of thepresent invention to a display portion are: a video camera; a digitalcamera; a goggle type display (head mounted display); a navigationsystem; an audio reproducing apparatus (car audio, an audio component,and the like); a laptop computer, a game machine; a portable informationterminal (a mobile computer, a cellular phone, a portable game machine,an electronic book, etc.); and an image reproducing apparatus includinga recording medium (specifically, an apparatus capable of processingdata in a recording medium such as a Digital Versatile Disk (DVD) andhaving a display device that can display the image of the data).Specific examples of the electronic apparatuses are shown in FIGS. 16Ato 16H.

FIG. 16A shows a television, which comprises a casing 2001, a supportingbase 2002, a display unit 2003, speaker units 2004, a video inputterminal 2005, etc. The present invention is applied to the display unit2003. The term television includes every television for displayinginformation such as one for a personal computer, one for receiving TVbroadcasting, and one for advertisement.

FIG. 16B shows a digital camera, which comprises a main body 2101, adisplay unit 2102, an image receiving unit 2103, operation keys 21404,an external connection port 2105, a shutter 2106, etc. The presentinvention is applied to the display unit 2102.

FIG. 16C shows a laptop computer, which comprises a main body 2201, acasing 2202, a display unit 2203, a keyboard 2204, an externalconnection port 2205, a pointing mouse 2206, etc. The present inventionis applied to the display unit 2203.

FIG. 16D shows a mobile computer, which comprises a main body 2301, adisplay unit 2302, a switch 2303, operation keys 2304, an infrared rayport 2305, etc. The present invention is applied to the display unit2302.

FIG. 16E shows a portable image reproducing apparatus equipped with arecording medium (a DVD player, to be specific). The apparatus comprisesa main body 2401, a casing 2402, a display unit A 2403, a display unit B2404, a recording medium (such as DVD) reading unit 2405, operation keys2406, speaker units 2407, etc. The display unit A 2403 mainly displaysimage information whereas the display unit B 2404 mainly displays textinformation. The present invention is applied to the display units A2403 and B 2404. The term image reproducing apparatus equipped with arecording medium includes domestic game machines.

FIG. 16F shows a goggle type display (head mounted display), whichcomprises a main body 2501, display units 2502, and arm units 2503. Thepresent invention is applied to the display unit 2502.

FIG. 16G shows a video camera, which comprises a main body 2601, adisplay unit 2602, a casing 2603, an external connection port 2604, aremote control receiving unit 2605, an image receiving unit 2606, abattery 2607, an audio input unit 2608, operation keys 2609, an eyepieceunit 2610, etc. The present invention is applied to the display portion2602.

FIG. 16H shows a cellular phone, which comprises a main body 2701, acasing 2702, a display unit 2703, an audio input unit 2704, an audiooutput unit 2705, operation keys 2706, an external connection port 2707,an antenna 2708, etc. The present invention is, applied to the displayunit 2703. If the display unit 2703 displays white characters on a blackbackground, power consumption of the cellular phone can be reduced.

As described above, the display device obtained by applying the presentinvention may be used as the display units of every electronicapparatuses. Since the stability of the performance of the displaydevice can be promoted and the design margin in the circuit design canbe expanded in the present invention, thus, a low-cost display devicecan be provided and the cost of parts for the electronic apparatus canbe lowered. Also, the electronic apparatuses of this embodiment may useany structure of the display devices shown in Embodiments 1 to 6.

According to the first aspect of the invention, by the process havinghigh design margin in circuit design, the display device can befabricated without dispersing threshold voltage of the thin filmtransistor and promotion of stability in the operational function of thedisplay device can be achieved. Further, the large capacity can beformed by the small area without particularly increasingphotolithography steps simultaneously with fabricating the thin filmtransistor and promotion of image quality of the display device can beachieved. Further, according to the second aspect of the invention, thefabricating process preferable in reducing the number of steps of thetechnology is provided and a reduction in fabricating cost in thedisplay device, particularly the light emitting device can be achieved.

What is claimed is:
 1. A method of fabricating a display devicecomprising the steps of forming a pixel electrode over a substrate, apart of the pixel electrode covered by a base film; forming asemiconductor film over the base film; forming a gate insulating filmover the semiconductor film; forming a gate electrode over the gateinsulating film; forming an impurity region in the semiconductor film;forming a first insulating nitride film over the gate electrode; formingan organic resin film over the first insulating nitride film; forming afirst opening portion in the organic resin film over the impurityregion; forming a second insulating nitride film to cover the firstopening portion; etching the second insulating nitride film, the firstinsulating nitride film and the gate insulating film at a bottom face ofthe first opening portion to form a second opening portion; forming awiring over the second insulating nitride film and connecting theimpurity region and the wiring through the first opening portion and thesecond opening portion, wherein in forming the first opening portion,the organic resin film is etched over the pixel electrode; wherein informing the second opening portion, the second insulating nitride film,the first insulating nitride film, the gate insulating film and the basefilm are etched so that the pixel electrode is exposed and the pixelelectrode and the wiring are electrically connected to each other afterthe pixel electrode is exposed.
 2. A method of fabricating a displaydevice comprising the steps of: forming a pixel electrode over asubstrate, a part of the pixel electrode covered by a base film; forminga semiconductor film over the base film; forming a gate insulating filmover the semiconductor film; forming a gate electrode over the gateinsulating film; forming an impurity region in the semiconductor film;forming a first insulating nitride film over the gate electrode; formingan acrylic film over the first insulating nitride film; forming a firstopening portion in the acrylic film over the impurity region; forming asecond insulating nitride film to cover the first opening portion;etching the second insulating nitride film, the first insulating nitridefilm and the gate insulating film at a bottom face of the first openingportion to form a second opening portion, forming a wiring over thesecond insulating nitride film and connecting the impurity region andthe wiring through the first opening portion and the second openingportion, wherein in forming the first opening portion, the acrylic filmis etched over the pixel electrode, wherein in forming the secondopening portion, the pixel electrode is exposed by etching the secondinsulating nitride film, the first insulating nitride film, the gateinsulating film and the base film are etched so that the pixel electrodeis exposed and the pixel electrode and the wiring are electricallyconnected to each other after the pixel electrode is exposed.
 3. Thedisplay device according to claim 1, wherein the organic resin film is aphotosensitive organic resin film.
 4. The display device according toclaim 2, wherein the acrylic film is a positive type photosensitiveacrylic film.
 5. The method of fabricating a display device according toclaim 1, wherein the first insulating nitride film and the secondinsulating nitride film each comprises a silicon nitride film, a siliconnitrooxide film, a silicon oxynitride film, an aluminum nitride film, analuminum nitrooxide film or an aluminum oxynitride film.
 6. The methodof fabricating a display device according to claim 2, wherein the firstinsulating nitride film and the second insulating nitride film eachcomprises a silicon nitride film, a silicon nitrooxide film, a siliconoxynitride film, an aluminum nitride film, an aluminum nitrooxide filmor an aluminum oxynitride film.
 7. The method of fabricating a displaydevice according to claim 1, wherein a radius of curvature at an upperend portion of the first opening portion falls in a range of 3 through30 μm.
 8. The method of fabricating a display device according to claim2, wherein a radius of curvature at an upper end portion of the firstopening portion falls in a range of 3 through 30 μm.
 9. The method offabricating a display device according to claim 1, wherein a radius ofcurvature at an upper end portion of the first opening portion ischanged continuously in a range of 3 through 30 μm.
 10. The method offabricating a display device according to claim 2, wherein a radius ofcurvature at an upper end portion of the first opening portion ischanged continuously in a range of 3 through 30 μm.
 11. The method offabricating a display device according to claim 1, wherein a contactangle θ at a lower end portion of the first opening portion is set to30°<θ<65°.
 12. The method of fabricating a display device according toclaim 2, wherein a contact angle θ at a lower end portion of the firstopening portion is set to 30°<θ<65°.
 13. A method of fabricating adisplay device comprising the steps of forming a pixel electrode over asubstrate; forming a base film over a part of the pixel electrode;forming a semiconductor film over a part of the base film; forming agate insulating film over the semiconductor film; forming a gateelectrode over the gate insulating film; forming an impurity region inthe semiconductor film; forming a first insulating nitride film over thegate electrode; forming an organic resin film over the first insulatingnitride film; forming a first opening portion in the organic resin filmover the impurity region; forming a second insulating nitride film tocover the first opening portion; etching the second insulating nitridefilm, the first insulating nitride film and the gate insulating film ata bottom face of the first opening portion to form a second openingportion; forming a wiring over the second insulating nitride film andconnecting the impurity region and the wiring through the first openingportion and the second opening portion: wherein in forming the firstopening portion, the organic resin film is etched over the pixelelectrode; wherein in forming the second opening portion, the secondinsulating nitride film, the first insulating nitride film, the gateinsulating film and the base film are etched so that the pixel electrodeis exposed and the pixel electrode and the wiring are electricallyconnected to each other after the pixel electrode is exposed.
 14. Themethod of fabricating a display device according to claim 13, whereinthe organic resin film is an acrylic film.
 15. The method of fabricatinga display device according to claim 13, wherein the first insulatingnitride film and the second insulating nitride film each comprises asilicon nitride film, a silicon nitrooxide film, a silicon oxynitridefilm, an aluminum nitride film, an aluminum nitrooxide film or analuminum oxynitride film.
 16. The method of fabricating a display deviceaccording to claim 13, wherein a radius of curvature at an upper endportion of the first opening portion falls in a range of 3 through 30μm.
 17. The method of fabricating a display device according to claim13, wherein a radius of curvature at an upper end portion of the firstopening portion is changed continuously in a range of 3 through 30 μm.18. The method of fabricating a display device according to claim 13,wherein a contact angle θ at a lower end portion of the first openingportion is set to 30°<θ<65°.